Bioprosthetic cardiovascular valve system

ABSTRACT

A cardiovascular valve system including a permanent base unit that is affixed to the patient using conventional sutures or staples, and a collapsible valve having a collapsible frame that mates with the permanent base unit, and supports valve leaflets. An installed collapsible frame may be re-collapsed and disengaged from the permanent housing. A new collapsible valve is then installed, to resume the function of the prosthesis.

RELATED APPLICATION

[0001] This is a continuation-in-part of U.S. application Ser. No.09/597,918, which is a continuation of International ApplicationPCT/U.S. Pat. No. 98/27,481, with an international filing date of Dec.23, 1998, which claims the benefit of U.S. Provisional Application No.60/068,711 filed Dec. 29, 1997.

BACKGROUND OF THE INVENTION

[0002] The current practice of inserting artificial heart valvesinvolves cutting the chest open, placing the patient on cardiopulmonarybypass, and surgically inserting the valve into an aorta. This processcan take several hours and subjects the patient to significant operativemortality. While the mortality during first valve replacement surgerycan be very low (less than 5%), the second surgery carries much greateroperative mortality, and the third is even more risky (>15%).Consequently, first and second re-operations to replace a worn outbioprosthetic heart valve are avoided. Since a typical bioprosthesis, ortissue valve, can wear out in 10 years, these valves are typicallyimplanted into patients 60 years old, or older. Younger patients areoften recommended a mechanical valve that does not wear out, andtypically does not need replacement.

[0003] Tissue valves, however, are often preferred over mechanicalvalves because of their better biocompatibility. Mechanical valves causeblood to clot on their components, and the patient must therefore bechronically treated with anticoagulants to eliminate the risk of majorblood clots. Anticoagulant themselves, however, carry a measurable riskof bleeding and thromboembolism and are not an ideal solution. Becausetissue valves do not need to be anticoagulated, they are potentially theideal valve prosthesis, if only their durability were to be improved.

[0004] Accordingly, the goal of most tissue valve research anddevelopment, has been the improvement in valve durability so that thesetissue valves can be put into patients younger than 60 or 65. Because ofthe operative mortality and morbidity, the objectives of all valveresearch and development, has been to increase the functional life spanof the bioprosthesis so that it can be put into patients only once, andwill last the life of the patient. This has thus far been an extremelydifficult goal to reach.

[0005] There may be another option, however, for the use of tissue heartvalves in the younger population. Rather than building valves that lastlonger, it may be more appropriate to build valves that can be routinelyreplaced in a way that induces negligible patient morbidity. Theobjectives would therefore be not to have extremely durable valves, butrather valves that can be easily removed when they begin to fail and newones inserted. The technologies that make this possible already existwith the advances made in the field of catheter-based endovascularprocedures, and the more broad field of Minimally Invasive Surgery(MIS).

[0006] The field of MIS is growing at an accelerating pace. The approachinvolves the use of small surgical probes, cannulas, video cameras andremote staplers and suture drivers that enable surgery to be donewithout requiring large incisions. Most MIS is done with several smallincisions, simply to allow the passage of these instruments into thepatients body. The principal advantages of MIS is that the patient issubjected to less surgical trauma and has a dramatically reducedhospital stay, which in turn significantly reduces the operating costsof the clinical center. Current generation minimally invasive proceduresare being carried out using endoscopes and long-reaching surgical tools.Typically, the patient's abdomen is inflated with carbon dioxide and theinstruments are inserted through small incisions. The surgeons thenperform the procedures using endoscopic visualization. Forcardiothoracic surgery, similar small incisions are created between theribs and the heart is placed on bypass using multiple cannulas withballoons that can selectively shut off blood flow through the heart, anddirect it through oxygenators.

[0007] Other technologies are being developed to do surgery on beatinghearts, as to completely avoid placing the heart on bypass. Many ofthese procedures involve the use of specialized catheters that deploydevices or tools that perform a wide range of procedures on the beatingheart. Typical beating heart procedures are endovascular balloondilatation of arteries and stent placement. Deployment of stents andother permanent devices has become commonplace, but to date, nosuccessful, catheter deployable valve has been developed.

[0008] While U.S. Pat. No. 5,545,214 discloses a balloon-deployabletissue valve, the technology is similar to that of stents, and is notideal for tissue heart valves. The material that anchors the valve inthe patient's aortic root is permanently deformed through the bending ofmetal components, and is not intended to be re-collapsed into itsoriginal configuration. Practically the same approach is disclosed inU.S. Pat. No. 5,411,552. U.S. Pat. No. 5,554,185 discloses a means ofdeploying the valve by inflating of a hollow valve frame with a liquidthat hardens. U.S. Pat. No. 5,545,209 describes the use of balloontechnology to permanently distend and deploy an endoprosthesis,typically a vascular segment for treating abdominal aneurysm. Thispatent makes reference to “a tubular prosthesis disposed on saidcatheter over at least a portion of said balloon.” U.S. Pat. No.5,855,601 describes a prosthetic valve affixed to a wire form that isself expanding, and has a plurality of barbs to anchor the stent in theaorta. The stent itself is of a continuous wire with a zigzagconfiguration, similar to the endoprostheses described above.

[0009] The major concepts disclosed by the above-mentioned patents aresimilar: the permanent deployment of a bioprosthetic heart valve. Apermanently deployed tissue heart valve, whether it is done using MIStechnology or not, is subject to the same requirements as conventionaltissue valves: it must be very durable. Good durability, however, is noteasily attained. The manufacturing process of tissue heart valves isvery mature and complex from the quality control point of view, and onlyminimal improvements in valve durability have been achieved in recentyears. Major improvements in valve durability are therefore not expectedin the near future.

[0010] The present invention addresses the drawbacks discussed above, aswell as other problems encountered with the prior art, to provide abioprosthetic cardiovascular valve system, wherein a valve can beinserted, removed, and re-inserted using minimally invasive surgicaltechniques.

SUMMARY OF THE INVENTION

[0011] According to one aspect of the present invention there isprovided a system for minimally invasive removal and re-insertion of abioprosthetic cardiovascular valve. Preferably, the valve issufficiently collapsible so as to be able to pass through the lumen of acatheter inserted into the femoral artery, or other large vessel. Thecollapsed valve is re-expanded when in place in order to fit into apermanent housing or base unit in the patients heart and assumes a fullyfunctioning state. Integral to this system of removal and replacement ofa prosthetic valve is an expandable “operative platform” that isdeployed near the site of the valve so that it stabilizes the cathetersand other instruments during the valve removal and reinsertion process.

[0012] In accordance with another aspect of the present invention, thereis provided a cardiovascular valve system comprised of a permanenthousing or base unit which remains in the patient, and a collapsiblevalve that engages with the permanent housing, and which is replaceable.

[0013] In accordance with a further aspect of the present invention,there is provided a permanent housing or base unit taking the form of anon-collapsible permanent frame which acts as a receptacle for thecollapsible valve. The permanent frame includes an integrated sewingring which is affixed to the patient's aorta or other tissue by means ofsutures or staples.

[0014] In accordance with another aspect of the present invention, thereis provided a collapsible cardiovascular valve including a collapsibleframe onto which several leaflets or flexible occluders are affixed,comprised of several articulating or hinged components which have asubstantially smaller perimeter when fully collapsed, than when fullyexpanded.

[0015] In accordance with still another aspect of the present invention,there is provided an inflatable or distensible “surgical platform” whichcan be delivered to a site near the heart in a collapsed state anddistended at that site such that it anchors the numerous catheters anddevices in space thereby ensuring proper controlled manipulation oftheir distal ends, when acted upon by controls at their proximal ends.

[0016] In accordance with still another aspect of the present invention,there is provided an integrated check valve within the surgical platformthat enables controlled ejection of blood from the ventricle during theprocess of collapsible valve removal and replacement.

[0017] In accordance with still another aspect of the present invention,there is provided an integrated filter within the surgical platform thatenables the capture of any particulates that may be released during theprocess of collapsible valve removal and replacement.

[0018] In accordance with yet another aspect of the present invention,there is provided a split wall or “monorail” catheter system which canguide larger instruments and devices between the outside of the patientand the surgical platform during the course of a valve replacementprocedure.

[0019] In accordance with yet another aspect of the present invention,there is provided a tracking and visualization system that can generateaccurate images or graphical representation of the catheters and othercomponents on a computer screen so as to accurately represent theposition of the real components inside the body of the patient.

[0020] Although the bioprosthetic collapsible valve of the presentinvention may incorporate various number of leaflets, a preferredembodiment of the valve incorporates three (3) valve leaflets.

[0021] Although the collapsible valve of the present invention mayincorporate a wide range of leaflet materials, such as syntheticleaflets or those constructed from animal tissues, a preferredembodiment of the valve incorporates three (3) valve leafletsconstructed from sheets of chemically preserved bovine pericardium.

[0022] Although the non-collapsible permanent frame may be constructedfrom a wide range of materials including metals and plastics, apreferred embodiment of the permanent frame is constructed from agenerally stiff, rigid material such as stainless steel, or a polymer.

[0023] Although the collapsing mechanism of the collapsible frame mayincorporate various means of remaining expanded within the permanentframe of the housing or base unit, one preferred embodiment ofmaintaining the collapsible frame of the collapsible valve in itsexpanded state is by means of “snapping” the collapsible frame intoslots or clips and/or around protrusions during the expansion process.The collapsible frame is therefore held in an expanded position by meansof an interference fit between components.

[0024] Although the collapsible valve of the present invention may beexpanded by various means, a preferred embodiment of the valve expandingmeans incorporates an articulating expanding means that does not requirethe use of balloon technology to expand the collapsible frame.

[0025] Although the collapsible frame of the present invention may becollapsed by various means, one embodiment of the valve collapsing meansinvolves expansion beyond its resting configuration, thus unsnapping itfrom the permanent frame, using a catheter-based manipulation means orhand-held tools.

[0026] Although the present invention may make use of numerous means ofstabilizing the proximal ends of the catheters, a preferred embodimentof the procedure is the use of a stabilizing surgical platform that canbe anchored distal to the aortic valve. The surgical platformincorporates slots and fixtures for attaching and holding catheters inslots that stabilize the movement and position of the distal ends of thecatheters so that deflection and manipulation of the catheter ends isdone in a controlled way.

[0027] Although the present invention may make use of numerous means oftemporarily augmenting the action of the contracting heart by means ofvalves, a preferred embodiment of the procedure is the incorporation ofan integrated check valve within the surgical platform that becomesfunctional once the platform is expanded in place. The integrated checkvalve can be fabricated out of polymer and have one or more occludingleaflets. The leaflets are soft and pliable and enable the passage ofcatheters and other devices past and through the leaflets. The surgicalplatform itself can be partially deflated during the valve replacementprocedure in order to allow catheters to slide past it to remove ordeliver a collapsed valve. The surgical platform may also incorporate anintegral sieve or screen to capture and hold any particulates that maybe liberated during a valve replacement procedure. The surgical platformmay also incorporate an optical, ultrasound, radiographic, magneticimaging head, or the like, so that close-up detailed images may beobtained during the valve replacement procedure.

[0028] Although the present invention may make use of numerous cathetersto deliver the components of the collapsible valve system into thedesired site, one embodiment of the procedure is the use of multiplecatheters and sheaths small enough to be inserted into the femoralartery without exposing the femoral artery to perform a “cut-down”.

[0029] Although the present invention may make use of numerous imagingor localization techniques, one preferred embodiment of the procedure isthe use of a ultrasonic or electromagnetic sensors affixed to thecatheters and components such that their position can be detected andtracked in 3-D space, in sufficient spatial and temporal resolution andprecision, so as to make the procedure easy and accurate. Anothervisualization technique is bi-plane radiography or intra-cardiacechocardiography.

[0030] As can be seen by those skilled in the art, an advantage of thepresent invention is the provision of a valve system that allows forsafe and convenient removal and replacement of a collapsible valve whenit begins to fail.

[0031] Another advantage of the present invention is the provision of anexpandable, re-collapsible tissue-based cardiovascular valve.

[0032] Another advantage of the present invention is the provision of anexpandable, re-collapsible valve that is small enough to be delivered bycatheters by way of a percutaneous puncture.

[0033] Another advantage of the present invention is the replacement ofa re-collapsible valve by way of conventional or minimally invasivecardiac surgery.

[0034] Still another advantage of the present invention is the provisionof a catheter-based valve delivery system.

[0035] Still another advantage of the present invention is the provisionof a valve delivery system consisting of surgical tools that can removeand deliver a re-collapsible valve by way of small incisions in theblood vessels that emerge from the heart, or in the wall of the heartitself.

[0036] Still another advantage of the present invention is the provisionof a stable surgical platform within which catheter-based manipulatorscan be securely anchored so that intracardiac procedures can be properlyexecuted.

[0037] Yet another advantage of the present invention is the provisionof a synthetic valve integrated with the surgical platform to act as atemporary check valve while the expandable, re-collapsible tissue-basedcardiovascular valve is being replaced.

[0038] Yet another advantage of the present invention is the provisionof a mesh integrated with the surgical platform to act as a sieve thatcaptures any particulates that may be liberated during the valvereplacement procedure.

[0039] Yet another advantage of the present invention is the provisionof a slotted catheter sheath that can act as a “monorail” guide toshuttle components along the outside of the sheath between theexit/entry port of the patient and the surgical platform within theheart.

[0040] Yet another advantage of the present invention is the provisionof a ultrasound or electromagnetic catheter guidance system that cantrack the position and motion of the catheters and devices during theprocedure and display images of the system components on a video displaymonitor, so as to make the procedure easy and accurate.

[0041] Still other advantages of the invention will become apparent tothose skilled in the art upon a reading and understanding of thefollowing detailed description, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The invention may take physical form in certain parts andarrangements of parts, a preferred embodiment and method of which willbe described in detail in this specification and illustrated in theaccompanying drawings which form a part hereof, and wherein:

[0043]FIG. 1 shows images of typical prior art bioprosthetic valvehaving leaflets made of bovine pericardium mounted on a supportingstent;

[0044]FIG. 2 shows a top plan view of the permanent frame, according toa preferred embodiment of the present invention;

[0045]FIG. 3A shows a perspective view of the collapsible frame inaccordance with a preferred embodiment of the present invention, in anexpanded position;

[0046]FIG. 3B shows a top plan view of the collapsible frame shown inFIG. 3A;

[0047]FIG. 3C shows a top plan view of the collapsible frame shown inFIG. 3A, in a collapsed position.

[0048]FIG. 4A illustrates a collapsible frame in an expanded position,in accordance with an alternative embodiment.

[0049]FIG. 4B illustrates the collapsible frame of FIG. 4A, in acollapsed position.

[0050]FIG. 5 shows an enlarged partial sectional view of the collapsibleand non-collapsible permanent frames, to illustrate the mating surfacesthereof;

[0051]FIG. 6A shows an exemplary embodiment of a valve collapsingcatheter;

[0052]FIGS. 6B and 6C show an exemplary embodiment of a valve expandingcatheter;

[0053]FIG. 7A shows an exploded view of a catheter-based valve deliverysystem, including a surgical platform and numerous accessory devices andcatheters, according to one preferred embodiment of the presentinvention;

[0054]FIG. 7B shows an enlarged partial sectional view of a slottedcatheter sheath, according to a preferred embodiment of the presentinvention;

[0055]FIG. 7C shows an enlarged partial sectional view of an innercatheter, according to a preferred embodiment of the present invention;

[0056]FIG. 7D is a schematic representation illustrating the operationof gripping means, in accordance with a preferred embodiment of thepresent invention;

[0057]FIG. 7E illustrates a surgical platform having a check valve, inaccordance with a preferred embodiment of the present invention;

[0058]FIG. 8A shows an alternative embodiment of an expandable surgicalplatform;

[0059]FIG. 8B is a schematic representation illustrating operation ofthe expandable surgical platform shown in FIG. 8A;

[0060]FIG. 9A illustrates a front view of the cardiac anatomic site;

[0061]FIG. 9B illustrates a top view of the cardiac anatomic site shownin FIG. 9A;

[0062]FIG. 9C is a simplified enlarged front view of the cardiacanatomic site shown in FIG. 9A.

[0063]FIG. 10 shows a top plan view of a permanent base unit, accordingto an alternative embodiment of the present invention.

[0064]FIG. 11 shows a perspective view of the permanent base unit, asshown in FIG. 10.

[0065]FIG. 12 shows a perspective view of a collapsible frame (in anexpanded position) of a collapsible valve, according to an alternativeembodiment of the present invention.

[0066]FIG. 13 shows a side view of the collapsible frame, as shown inFIG. 12.

[0067]FIG. 14 shows a perspective view of the collapsible frame of FIGS.13 and 14 (in a collapsed position), according to an alternativeembodiment of the present invention.

[0068]FIG. 15 shows a perspective view of the collapsible frame of FIGS.12-14, in an expanded configuration, as an engaged with the permanentbase unit shown in FIGS. 10 and 11.

[0069]FIG. 16 shows a perspective view of the collapsible cardiovascularvalve in its expanded position (including the collapsible frame of FIGS.12-14 and two valve leaflets, wherein the third valve leaflet is omittedfor clarity).

[0070]FIG. 17 shows a perspective view of the cardiovascular valvesystem according to an alternative embodiment of the present invention,wherein the collapsible valve (including the collapsible frame of FIGS.12-14 and two valve leaflets, wherein the third valve leaflet is omittedfor clarity) is shown in an expanded position, as engaged with thepermanent base unit shown in FIGS. 10 and 11.

[0071]FIG. 18A shows a perspective view illustrating one method by whichvalve leaflets are connected with a collapsible frame.

[0072]FIG. 18B shows a perspective view illustrating another method bywhich the valve leaflets are connected with a collapsible frame.

[0073]FIG. 18C shows a perspective view illustrating still anothermethod by which valve leaflets are connected with a collapsible frame.

[0074]FIG. 19A shows a partial perspective view illustrating a method bywhich a collapsible frame of the collapsible valve is engaged with apermanent frame of the permanent base unit.

[0075]FIG. 19B shows a partial perspective view illustrating anothermethod by which a collapsible frame of the collapsible valve is engagedwith a permanent frame of the permanent base unit.

[0076]FIG. 19C shows a partial perspective view illustrating stillanother method by which a collapsible frame of a collapsible valve isengaged with a permanent frame of the permanent base unit.

[0077]FIG. 20A shows a cross-sectional view taken along line A-A of FIG.19A.

[0078]FIG. 20B illustrates yet another alternative method by which acollapsible frame of a collapsible valve is engaged with a permanentframe of the permanent base unit.

[0079]FIG. 21 shows a perspective view of a cardiovascular valve systemcomprised of a collapsible valve (including the collapsible frame ofFIGS. 12-14 and two valve leaflets, wherein the third valve leaflet isomitted for clarity) and a permanent base unit, according to stillanother alternative embodiment, wherein the collapsible frame is fittedover the permanent frame.

[0080]FIG. 22 illustrates a cardiovascular valve system according toanother alternative embodiment.

[0081] FIGS. 23A-23C and 24 illustrate operation of a retaining clip ofthe cardiovascular valve system shown in FIG. 22.

[0082]FIG. 24 illustrates the cardiovascular valve system according tothe alternative embodiment of FIG. 22, showing the collapsible valvefitted over a catheter body and snares positioned over retaining clips.

[0083]FIG. 25A shows a cross-sectional view of a collapsible valvefitted over a catheter body of a positioning catheter.

[0084]FIG. 25B shows a cross-sectional view of a catheter body of apositioning catheter.

[0085]FIG. 25C illustrates a contact area for the outer surface of acatheter body and a portion of a collapsible valve.

[0086]FIGS. 26A and 26B illustrate a valve expanding catheter 160.

[0087]FIGS. 26C and 26B illustrate a procedure for expanding acollapsible valve for installation thereof, in accordance with thealternative embodiment shown in FIG. 22.

[0088] FIGS. 27A-27C illustrate a cardiovascular valve system accordingto yet another alternative embodiment.

[0089]FIGS. 28 and 29A-29C illustrate operation of an expanding leverfor disengaging a collapsible valve from a base unit.

[0090] FIGS. 29D-29G illustrate the yet another alternative embodimentof engaging a collapsible valve to a base unit.

[0091]FIG. 30 illustrates use of a valve collapsing catheter inconnection with the cardiovascular valve system of FIG. 27A.

[0092]FIGS. 31A and 31B illustrate a surgical platform according to analternative embodiment of the present invention, wherein a screen isincorporated to trap particulates (FIG. 31A), and a synthetic valve isincorporated to control the flow of blood (FIG. 31B).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0093] The detailed description set forth below in connection with theappended drawings is intended merely as a description of the presentlypreferred embodiments of the invention, and is not intended to representor limit the form in which the present invention can be constructed orused. The description sets forth the function and sequence of steps forconstruction and implementation of the invention. It is to be understoodthat the same or equivalent functions and sequences may be accomplishedby different embodiments that are also intended to be encompassed withinthe spirit and scope of the invention. For example, a similar valvesystem can be used to insert a similar collapsible valve (e.g., aprosthetic valve or endoprosthesis) into the mitral position, thepulmonary and tricuspid positions of the heart or an other expandableprosthetic device into any other location within the vasculature or anorgan of any patient. Moreover, while a preferred embodiment of thepresent invention is illustrated herein as a cardiovascular valve systemfor use in connection with the heart, the present invention iscontemplated for use as a valve system with other parts of thecardiovascular system.

[0094] In accordance with a preferred embodiment of the presentinvention, a system for inserting a valve into the aortic position usinga catheter-based, endovascular, minimally invasive techniques isgenerally comprised of the following:

[0095] (1) A valve that can be collapsed for insertion, expanded when inplace so as it fits securely within a permanent housing that remains inthe patient, and collapsed again for removal once the tissue componentof the collapsible valve wears out.

[0096] (2) A multi-component, catheter-based system for thepercutaneous, removal and delivery of a collapsible valve.

[0097] (3) A set of surgical tools that have fixtures similar to thoseat the ends of the catheters, for the surgical removal and delivery of acollapsible valve.

[0098] (4) A device tracking, visualization system to enable thisprocedure to be done with high precision and minimal chance ofcomplications.

I. Construction of the Collapsible Cardiac Valve and Frame

[0099] One aspect of the present invention is directed to an expandable,re-collapsible tissue-based valve system. With reference to FIG. 1 atypical prior art tissue-based prosthetic valve includes three (3)leaflets 13 sewn to and supported on a metal or polymer frame or stent11. One aspect of the present invention is directed to a collapsiblevalve system generally comprised of two components: (i) a permanentouter frame that is affixed to the patient using conventional sutures orstaples (FIG. 2), and (ii) an inner collapsible valve (FIGS. 3A-3C and4A-4B) that mates with the outer frame and includes valve leaflets. Theinner collapsible valve is normally collapsed, is delivered against thepreviously inserted outer frame, expanded, and locked in place.Importantly, the inner collapsible valve may be collapsed again andremoved. A new inner collapsible valve is then inserted into theoriginal outer frame, to resume the function of the prosthesis.

[0100] With reference to FIG. 2, there is shown a preferred embodimentof a permanent base unit taking the form of an outer frame 10. Outerframe 10 is generally comprised of a rigid ring 11, and a soft sewingring 12 for attachment of the outer frame 10 the wall of the aorta orother structure within the heart.

[0101] Referring now to FIGS. 3A-3B and 4A-4B, there is shown apreferred embodiment of the collapsible valve 20. Collapsible valve 20is generally comprised of an articulating inner frame 21 having aplurality of projections or stent posts 22, and a plurality of leaflets(not shown). It should be understood that the leaflets are mounted tothe stent posts 22 in a manner similar to that shown in FIG. 1, andmovable between an occluded position and an open position. The innerframe 21 that supports the plurality of leaflets is formed of aplurality of articulated segments 24 (typically 6 or more segments),that fold together in a way so that the total outer diameter of theinner frame is reduced for insertion, as best seen in FIG. 3C. Thearticulated segments 24 are typically rigid structures that snap into alocked position as they are completely unfolded during deployment.Articulated segments 24 articulate around pin hinges 25 (FIGS. 3B-3C) orother flexible strips 28 (FIGS. 4A-4B), means that can assure a flexibleattachment between any adjacent segments. It will be appreciated thatother means for articulating are also suitable, including ball andsocket joints.

[0102] The process of collapse and expansion involves a “snapping”action that produces some elastic material deformation of the segments24 and/or the hinges 25 and/or the strips 28, as the segments articulatebetween their fully expanded configuration and their partially collapsedconfiguration. This is achieved by means of an interference fit betweenopposing segments that articulate near each other. The provision for thesnapping process is so that once expanded, the inner frame remainsexpanded under its own internal tension, and does not collapse due toundue internal or external force applied to it during normal activity.

[0103] Referring now to FIG. 5, the inner frame 21 is held in tightopposition against the rigid ring 11 of the outer frame 10 by means of agenerally annular groove 14 on the inner surface of the rigid ring 11,into which each of the articulating segments 24 fit when the inner frame21 is expanded. Accordingly, annular groove 14 provides a means forinterfacing and attaching outer frame 10 with inner frame 11. It will beappreciated that articulated segments 24 include a flange portion 23,which is dimensioned to be received into groove 14. The fit betweenflange portion 23 of inner frame 21 and groove 14 of rigid ring 11 issuch that the collapsible valve 20 cannot be withdrawn from the outerframe 10 when the inner frame 21 is expanded, and can only be withdrawnwhen the inner frame 21 is collapsed. It should be appreciated thatother means for interfacing inner frame 21 with outer frame 10 are alsosuitable.

[0104] A collapsible cardiovascular valve system according to analternative embodiment of the present invention will now be describedwith reference to FIGS. 10-20. Referring to FIGS. 10 and 11, there isshown a permanent base unit 100 according to an alternative embodimentof the present invention. Permanent base unit 100 is generally comprisedof a permanent frame 102 and a generally annular soft sewing ring 104.Sewing ring 104 is used to attach permanent base unit 100 with the wallof the aorta or other structure within the heart, as well known to thoseskilled in the art. Permanent frame 102 includes a generally circulararrangement of outward extending generally triangular flat rigid plates103, which when arranged circumferentially, define a valve orifice. Agenerally v-shaped opening is defined by adjacent pairs of plates 103.Permanent frame 102 acts as a receptacle for a collapsible valve,described below.

[0105] A collapsible valve 109 according to an alternative embodiment ofthe present invention will now be described with reference to FIGS.12-17. Collapsible valve 109 is generally comprised of an collapsibleframe 110 and at least one valve leaflet 120. FIGS. 12-15 illustratecollapsible valve 109 without valve leaflets 120, in order to moreclearly illustrate collapsible frame 110. Furthermore, FIGS. 12-13 and15-17 illustrate collapsible valve 109 in an expanded position, whileFIG. 14 illustrates collapsible valve 109 in a collapsed position.

[0106] Collapsible frame 110 is generally comprised of a plurality ofarticulating generally linear rigid struts 112 connected together attheir distal ends 136 by way of an articulation member 114. Struts 112fold together in a manner to minimize the total outer diameter ofcollapsible frame 110 in a collapsed position, to facilitate insertionand removal of valve 109.

[0107] Articulation member 114 preferably includes (but is not limitedto) pivot members, pin hinges 25 (such as shown in FIGS. 3B-3C),flexible strips 28 (such as shown in FIGS. 4A-4B), ball and socketjoints, or other means that allow for a flexible articulation betweenadjacent struts 112.

[0108] As illustrated in FIGS. 15-17, collapsible frame 110 may beengagingly opposed against the inner surface of rigid plates 103 when itis in an expanded position. In this regard, plates 103 are dimensionedto correspond with the dimensions of collapsible frame 110 in itsexpanded position. Accordingly, the profile formed by plates 103 ismatched to correspond to the profile formed by collapsible frame 110when collapsible frame 110 is in an expanded position. Thus, struts 112of collapsible frame 110 abut the inner surface of plates 103 (FIG. 15).If collapsible frame 110 is comprised of six rigid struts 112 (as bestshown in FIGS. 12-13), then permanent frame 102 is comprised of sixappropriately-sized plates 103. In accordance with a preferredembodiment, three valve leaflets 120 (only two are shown for clarity inFIGS. 16 and 17) are suspended from collapsible frame 110. Thus, whencollapsible frame 110 is expanded, a fully functioning valve is formed.

[0109] Referring now to FIGS. 18A-18C, there are shown severalalternative approaches for attaching valve leaflets 120 to collapsibleframe 110. These approaches include valve leaflets 120 affixed to struts112 by wrapping valve leaflets 120 over the top upper surface of struts112 (FIG. 18A), under the bottom lower surface of struts 112 (FIG. 18B),or into a slot 124 formed in struts 112 (FIG. 18C). Valve leaflets 120may be connected to struts 112 by way of sutures passing through holesformed in struts 112, or by way of pins or tacks, either individual orpart of a strip of material 126, that pass through leaflet 120, andinsert and lock into strut 112 (FIG. 18A). It should be appreciated thatstruts 112 of collapsible frame 110 mate tightly against plates 103(FIGS. 15 and 17) in the expanded position, so as to prevent any bloodfrom leaking between struts 112 and plates 103.

[0110] As will now be described with reference to FIGS. 19A-19C, thereare several alternative methods by which collapsible frame 110 may beretained in tight opposition against plates 103 of permanent frame 102.These approaches include (but are not limited to) a provision for struts112 to be positioned and attached to: (a) the inner surface of plates103 (FIG. 19A), (b) the outer surface of plates 103 (FIG. 19B ), or (c)the top edge of plates 103 (FIG. 19C). In each approach, struts 112 arein engaged with plates 103, thus preventing blood from leaking betweenthem.

[0111] Struts 112 may be retained by appropriately shaped supports orgussets 116 that project from the surface of plates 103, either alongthe entire length of contact between strut 112 and plate 103, or onlypart of the way (FIGS. 19A and 19B). FIG. 20A provides a cross-sectionalview of permanent frame 102 taken along line A-A of FIG. 19A. Gusset 116is shown affixed to the inner surface of plate 103. As can be seen inFIG. 20A, gusset 116 is dimensioned such that it accepts strut 112 bymeans of a snap fit. A similar gusset 116 is affixed to the outersurface of plate 103 in the embodiment shown in FIG. 19B.

[0112] In the embodiment shown in FIG. 19C struts 112 are slotted alongtheir length, so as to fit onto the top edge of plate 103, anappropriately sized slot 118 is formed in struts 112. In this regard,slots 118 act to retain collapsible valve 109 in engagement withpermanent frame 102. It should also be appreciated that plates 103 areappropriately dimensioned at their top edge to provide the necessaryclearance, so as not to cause interfere with articulation member 114.

[0113]FIG. 20B illustrates yet another alternative means for engagingstruts 112 with permanent frame 102. In this regard, plates 103 aredimensioned to be sufficiently thick such that a channel 117 can beformed in the top edge thereof. Channel 117 is dimensioned to receivestrut 112 by means of a snap fit, thus retaining collapsible valve 109in engagement with permanent frame 102. Struts 112 are received intochannels 117 formed in the top edge of plates 103, thus securingcollapsible frame 110 to the top edge of plates 103 in a manner similarto the embodiment shown in FIG. 19C.

[0114] Referring now to FIG. 21, there is shown another embodiment ofbase unit 100, wherein permanent frame 102 includes holding plates 130that are positioned adjacent to rigid plates 103, to form a slot or gapfor receiving strut 112. Holding plates 130 capture and hold in placethe bottom ends of struts 112 of collapsible frame 110, in theembodiment wherein struts 112 of collapsible frame 110 are engaged withthe outside of rigid plates 103, such as shown in FIG. 19B. In thisregard, hold plates 130 act as additional retainers for retainingcollapsible valve 109 in engagement with permanent frame 102.

[0115] Referring now to FIGS. 22-24, there is shown yet anotheralternative embodiment of the cardiovascular valve system, wherein yetanother means is used for retaining collapsible valve 109 in engagementwith permanent frame 102. In addition to using holding plates 130 tocapture and hold in place the bottom ends of struts 112 (as in theembodiment shown in FIG. 21), a channel 117 may be formed along some orall the length of the upper surface of plates 103 of permanent frame102. Channel 117 is dimensioned to receive struts 112 of collapsibleframe 110. A plurality of retaining clips 140 are provided to securestruts 112 within channel 1 17. Retaining clips 140 are movable betweena retain position and a release position, and are biased to the retainposition. In the retain position, struts 112 are retained within channel117. In a release position, struts 112 may be removed from channel 117,or inserted into channel 117. Preferably, retaining clips are formed ofan elastic material to facilitate movement between the retain andrelease positions.

[0116] With particular reference to FIGS. 23A-23C, it can be seen thatretaining clips 140 are located adjacent the inner surface of plates 103at lower end 142 thereof, and include a projection portion 144 whichprojects up and over the top surface of struts 112, at ends 136 thereof.Projection portion 144 may have a generally curved shape. Projectionportion 144 prevent struts 112 from disengaging from channel 117 byprojecting over the top surface of strut 112 at end 136. Consequently,collapsing collapsible frame 110 requires retaining clip 140 to beelastically bent away from the inner surface of plate 103 (i.e., movedto a release position) so as to allow struts 112 to be disengaged fromchannel 117 (FIG. 23B).

[0117]FIG. 23C illustrates an exemplary method for bending retainingclip 140 away from the inner surface of plate 103. In this regard, asuitable snare 32 is engaged with a recess or notch 146 formed at thedistal end of projection portion 144. Snare 32 applies tension toprojection portion 144 by being pulled back into a catheter 31 (see FIG.6A). Notch 146 is dimension so as to prevent snare 32 from slipping outduring all possible angles of function.

[0118] The process by which retaining clips 140 are captured by snares32 and pulled to a release position by drawing the snares into acatheter body 31, will now be described with reference to FIG. 24. Itshould be appreciated that collapsible valve 109 may be fitted overcatheter body 31, prior to being expanded and fitted to permanent baseunit 100. Collapsible valve 109 may be fitted over catheter body 31 in avery compact, space efficient way.

[0119] Referring now to FIGS. 27-29, there is shown yet anotheralternative embodiment of the cardiovascular valve system. Yet anothermeans is used to retain the collapsible valve 109 in engagement withpermanent frame 102. In accordance with this embodiment of thecardiovascular valve system, struts 112 of collapsible frame 110 arefitted against the outer surface of the plates 103, as in FIG. 19B. Inaddition to using holding plates 130 to capture and hold in place thebottom ends 136 of struts 112 (as in the embodiment shown in FIG. 21),base unit 100 is fitted with retaining members 140′ that protrude overthe top ends 136 of struts 112. In accordance with a preferredembodiment, retaining members 140′ are comprised of two generallyperpendicular portions. Unlike the deflectable retaining clips 140 ofFIG. 23, retaining members 140′ are generally rigid and affixed toplates 103 of permanent frame 102.

[0120] As shown in FIG. 27A, top ends 136 of struts 112 of collapsiblevalve frame fit underneath these retainers. The retaining members 140′therefore prevent collapsible frame 110 from disengaging from the baseunit 100. Collapsible frame 110 is provided with a plurality of pivotinghooks 180, that rotate about a cylindrical portion of the top ends 136of struts 112, as best shown in FIG. 28. This Figure shows a detailedview of the top end of a strut 112, showing a horizontal cylindricalportion 184 of the top end 136 of a strut 112. Cylindrical portion 184joins a pair of adjacent struts 112. Two sets of articulation members114 are provided at the top end 136 of a strut 112, rather than a singlearticulation member 114 that is present at the bottom end of a strut112.

[0121] With reference to FIGS. 29A-29C, it can be seen that hooks 180have a generally curved shape and project outward from collapsible frame110, such that they can be captured by snares 32. Operation of hooks 180will be described below.

[0122] Referring now to FIG. 29D and FIGS. 29E-29G, there is shown yetanother alternative embodiment of the cardiovascular valve system. Yetanother means is used to retain collapsible frame 110 in engagement withpermanent frame 102. FIGS. 29E, 29F and 29G respectively illustrateside, front and top views. In accordance with this embodiment of thecardiovascular valve system, struts 112 of collapsible frame 110 includea clip 188 that projects generally inward, towards the center of thevalve and engages with post 186 that projects generally upward from topend of plates 103 of permanent frame 102. Clip 188 includes a recess orcut-out 189 that is dimensioned to receive post 186, to provideengagement therebetween. Post 186 also includes an enlarged portion orcollar 187 having a largest dimension that is greater than the largestdimension of cut-out 189, thus inhibiting clip 188 from sliding upwardsalong post 186. This prevents collapsible valve 109 from disengagingfrom permanent frame 102. Collapsible valve 109 disengages frompermanent frame 102 by deflection, caused by the action of hooks 180, aswill be described below. Post 186 may also be suitably fitted with ahook at its end for capturing snares, if desired.

[0123] Referring now to FIG. 25A, there is shown a cross-sectional viewof a collapsible valve 109 fitted over a distal catheter body 31 of apositioning catheter 33. As discussed above, a preferred embodiment ofcollapsible valve 109 includes a collapsible frame 110 having six rigidstruts 112, to which three valve leaflets 120 are affixed. In theembodiment shown in FIG. 25A, the valve leaflets 120 are affixed tostruts 112 by way of a strip of tacks 126.

[0124]FIG. 25B shows a cross-sectional view of a catheter body 31 of apositioning catheter 33, which is generally comprised of a generallycircular polymer extrusion, (with a distal end that engages with thecollapsible valve 109) has a number of flat facets 34. Facets 34 enablecollapsible valve 109 to mate against the outer surface of catheter body31. As shown in FIG. 25C, articulation member 114 at end 136 of struts112 contacts with outer surface of catheter body 31 in a contact area150. In accordance with a preferred embodiment, catheter body 31 has atleast as many facets 34 as there are contact areas 150 betweencollapsible valve 109 and catheter body 31. It should be understood thatthe number of contact areas 150 is defined by the number andconfiguration of struts 112.

[0125] In accordance with a preferred embodiment of the presentinvention, catheter body 31 has a plurality of generally oval channels36 and a plurality of generally round channels 38. Oval channels 36 aredimensioned to accommodate the loop of wire for the snares 32, whileround channels 38 are dimensioned to accommodate pull wires to steer thecatheter. A central lumen 37 may also be provided so as to enablecatheter body 31 to be directed to the appropriate site by way of aguide wire.

[0126] Referring now to FIG. 30, there is shown an alternativeembodiment of a valve collapsing catheter 30′, including a catheter body31 and preformed snares 32. In this embodiment, catheter body 31 issplit into three segments 35. Snares 32 are fitted into each segmentsuch that the two ends of snare 32 are drawn inward into differentsegments 35. This embodiment has the advantage of providing a nearlycircular snare that can be more easily positioned over hooks 180 ofcollapsible frame 110.

II. Collapse and Expansion of the Collapsible Cardiac Valve

[0127] During most of its useable life span, the collapsible valve 20remains in its expanded state. The collapse of the inner frame 21 may becarried out with a remote manipulating device, such as valve collapsingcatheter 30 (FIG. 6A) that includes one or more snares that grabs ontoprojections 26 or “handles” formed on the collapsible inner frame 21(FIGS. 3A-3C). The valve collapsing catheter 30 includes a catheter body31 and a plurality of cables preformed to conveniently sized loops orsnare means 32. The snare means 32 can be extended from the catheterbody 31 to preformed shapes, such that they can grab onto theprojections 26 of the collapsible inner frame 21. When the snare means32 are pulled back into the lumen of the catheter body 31, an inwardforce is achieved, sufficiently strong to “snap” the collapsible innerframe 21 into its collapsed position.

[0128] In the case of the alternative embodiment of the cardiovascularvalve system described above with reference to FIGS. 10-30, the processof collapse may need to involve initial expansion, if collapsible frame110 is configured as to be on the outside of plates 103, as shown inFIGS. 19B, 21 and 27-30. Since normal cardiac loads imposed on leaflets120 of the closed valve are directed downwards and inwards, struts 112of collapsible frame 110 are held tight against the outer surface ofplates 103. Collapse of collapsible frame 110 therefore requires the topend 136 of struts 112 to be pushed outward during removal of collapsibleframe 110 from permanent base unit 100. This prevents collapsible frame110 from collapsing and disconnecting itself from plates 103 duringnormal valve function. The snap-in gussets 116 shown in FIGS. 20A and20B are another such feature, in the case where collapsible frame 110 isconfigured to be positioned adjacent to the inner surface of plates 103,as shown in FIG. 19A.

[0129] The process of expansion of the inner frame 21 is opposite to thecollapsing process. Referring now to FIGS. 6B and 6C, there is shown asuitable remote manipulating device for expanding the inner frame 21.Valve expanding catheter 40 includes a catheter body 41 and anarticulating system 43 at its end that pushes against the projections 26or some convenient segments 24 in order to expand the inner frame 21 andproperly seat it in the outer frame 10. Valve expanding catheter 40includes an inner rod 42 that slides in when pulled or pushed upon atits proximal end. Articulating system 43 is located at the distal end ofinner rod 42, and includes a number of articulating arms or levers thathinge such that they expand when the inner rod 42 is drawn inwards. Thisaction generates an outward push upon the inner frame 21 so that itexpands and snaps into place in the rigid ring 11 of the outer frame 10.Because of the fit between the inner frame 21 and the rigid ring 11, theinner frame 21 cannot be separated from the outer frame 10 whenexpanded, and can only be separated when the inner frame 21 is in thecollapsed position. Accordingly, the collapsible valve 20 safelyoperates when the inner frame 21 is in the expanded position.

[0130] It should be understood that in the embodiments shown in FIGS.10-25, the process of valve expansion and installation involves severalco-axial catheters. Referring now to FIGS. 26A and 26B, there is shown avalve expanding catheter 160, which includes a catheter body 162 and avalve expander assembly 164 located at the distal end thereof. FIG. 26Aprovides a partially exploded view of valve expanding catheter 160.Valve expander assembly 164 includes a plurality of generally rigid legs166. The distal end of each leg 166 is fitted with a strut clip 168 thatcan be snapped over the top of articulation member 114 at end 136 ofstruts 112 (FIG. 26A). The proximal end of each leg 166 is connectedwith a pusher ring 170, which is connected with a catheter body 162.Legs 166 fit into pusher ring 170 by way of slots 172 that helpstabilize articulating motion of valve expander assembly 164. In apreferred embodiment, strut clips 168 pivot about legs 166 by way of pinjoints 174. Legs 166 pivot within pusher ring 170 by way of similar pinjoints 174. Valve expanding catheter 160 fits over a positioningcatheter 33, distal to a collapsed valve 109 (FIG. 26C).

[0131] The process of expansion and installation of collapsible valve109 will now be described in detail. First, notches 146 of projectionportion 144 are snagged using snares 32 (FIG. 23C and 24). Snares 32 arethen withdrawn into catheter body 31 (FIG. 24), which results in bendingretaining clips 144 away from plates 103 (FIGS. 23C and 24). Next, valveexpanding catheter 160 is pushed downward, causing collapsible valve 109to impinge on taut snares 32 and expand. Consequently, legs 166 andstrut clips 168 will pivot about pin joints 174 and articulate outward,as shown in FIGS. 26C and 26D. Once valve 109 has expanding such thatits diameter is greater than that of permanent base unit 100, struts 112will move downward into channels 117, best shown in FIG. 23. Once struts112 have been received into channels 117, tension applied to snares 32may be released, enabling projection portion 144 of retaining clips 140to move back to their retain position (FIG. 23A). As a result, struts112 are secured within channels 117. Expanding catheter 160 can then bewithdrawn upwards, unsnapping strut clips 168 from struts 112, and thusreleasing expanding catheter 160 from collapsible valve 109.

[0132] In the case of the alternative embodiment shown in FIG. 27A,FIGS. 29A-29C illustrate an exemplary method for disengaging collapsibleframe 110 from base unit 100. Hooks 180 are rotatable between anengagement position (FIG. 29A) and a disengagement position. With regardto disengagement, when the snares 32 are pulled upward back into acatheter 31(see FIG. 6A), hooks 180 rotate and act as a lever to deflectthe top ends 136 of struts 112 outward (i.e., away from base unit 100),thus expanding collapsible frame 110. Consequently, the top ends 136 ofthe collapsible frame 110 move past retaining members 140′, resulting inthe disengagement of collapsible frame 110 from base unit 100.

[0133] In the case of the alternative embodiment shown in FIGS. 29D-29G,rotation of hooks 180 acts to deflect top ends 136 of struts 112 outward(i.e., away from base unit 100), thus expanding collapsible frame 110.Consequently, clip 188 moves past collar 187, resulting in thedisengagement of collapsible frame 110 from base unit 100.

III. Intra cardiac Removal and Delivery of Collapsible Cardiac Valve

[0134] The system for collapse, removal and delivery of a replacementcollapsible valve makes use of novel catheter technologies. Acatheter-based valve delivery system must itself be collapsible so thatit can be inserted percutaneously, and deliverable by catheter to theappropriate site. In accordance with a preferred embodiment of thepresent invention, a catheter-based valve delivery system is generallycomprised of several catheters or catheter sheaths, that can shuttlecomponents in and out of the body to the desired spot with minimalrepositioning.

[0135] FIGS. 7A-7E illustrate components of a delivery system, accordingto a preferred embodiment of the present invention. The distal end ofthe delivery system is anchored in the ascending aorta, and is referredto herein as the surgical platform 50. All catheters C1, 53 and 57, andother valve manipulation devices have their distal ends anchored withinthe surgical platform 50, so that they can be stable at their distal endand perform their function with good control and accuracy. Thecatheters, themselves act as remote manipulators that can be controlledby pull wires, or by means of small actuators controlled electrically orhydraulically that deflect the catheters or in some way change theirshape. Since the objectives of some of the catheters is to deliver thecollapsible valve 20 and other components from the outside of thepatient to the operative site inside the patient, these catheters havean inner lumen through which pull cables and other catheters can slide.

[0136] The shuttling of larger objects between the outside world and thesurgical platform 50 is achieved by splitting the main guiding catheter53 along its length to form an elongated slot 55. Accordingly, mainguiding catheter 53 acts as a slotted catheter sheath for inner pullcables or an inner catheter 57. Inner catheter 57 has gripping means 54that project through slot 55 spanning the wall of the main guidingcatheter 53. Gripping means 54 attach collapsible valve 20 or otherdevices to inner catheter 57, and slide along slot 55, as will beexplained in detail below. Accordingly, the slotted main guidingcatheter 53 and inner catheter 57 provide a “monorail” system thatconveniently transports devices in and out of the body by moving themalong the length of the main guiding catheter 53.

[0137] Since the collapsible valve 20 and other devices may not fitinside a typical catheter, they must be delivered to the operative sitealong the outside of the main guiding catheter 53. Moreover, thecollapsible valve 20 needs to be passed through the surgical platform 50to the operative site, the slots 55 need to be continuous through thesurgical platform 50. Accordingly, the surgical platform 50 is fittedwith appropriate similar slots 56 so that the surgical platform 50 doesnot interfere with the passage of objects along the main guidingcatheter 53.

[0138] The main guiding catheter 53 is locked in place to the surgicalplatform 50 by means of a system, such as a twist or snap connector,that lines up the slot 55 of the main guiding catheter 53 with the slot56 formed in the surgical platform 50. Objects that are passed throughthe vasculature to the operative site, can be anchored to the innercatheter 57. In this regard, gripping means 54 may include a simple,spring-loaded clamp 59 that is held closed by a conventional coil spring51 (FIG. 7D). The spring 51 can be opened remotely simply by pushing theinner catheter 57 against the closed end 75 of the main guiding catheter53. This generates a pushing force on the clamp 59 and allows one of thejaws to rotate, thus opening the clamp and releasing the device. It willbe appreciated that gripping means 54 may take other suitable forms.

[0139] The surgical platform 50 can be fabricated from balloontechnology, as shown in FIG. 7A. Alternatively, as shown in FIGS. 8A and8B, a cylindrical surgical platform 60 can be formed from a wound stripof material that is held in a fitting 61 and unrolls by means of arotating shaft 62. This means of unwrapping or expanding the wound stripof material to increase its diameter structure, operates in a mannersimilar to the way that a “hose clamp” reduces its diameter, when beingwound up. The rotating shaft 62 can sit suspended within the fitting 61by means of bushings 63. The shaft 62 can deliver its torque to thewound strip of material through a friction contact, or by means of shortteeth or textured bumps 64, that engage with similar depression, pits,or slots 65 on the inner surface of the wound strip of material.

[0140] It should be appreciated that the delivery system, and inparticular the surgical platforms 50, 60 may also contain an auxiliarysynthetic check valve 70 (FIG. 7E) that cyclically opens and closes,replacing the function of the worn out collapsible valve while it isbeing removed and replaced with a new collapsible valve. The syntheticcheck valve 70 may be integrated into the lumen 58 of the surgicalplatform 50. The synthetic check valve 70 is comprised of a one or moreflaps of polymer that seal the lumen 58 when the check valve 70 isclosed, and move out of the way when the check valve 70 opens passivelyas blood is ejected from the heart. There is provision made for manuallyopening the check valve 70 by means of catheters and pull wires, so thatlarger objects can be passed by this check valve on the way to theoperative site. Alternatively, the action of the one-way check valve 70can be replaced by an occluding balloon that cyclically expands andcollapses under external control, and occludes the aorta distal to thesurgical platform.

[0141] In an alternative embodiment of surgical platform 50, a sieve ora screen 52 is provided that enshrouds the lumen 58 of the surgicalplatform (FIG. 31A). This sieve can be delivered in a collapsed, orrolled up state within the deliver catheter C1, and automaticallydeployed as the surgical platform is expanded. In the case where thesieve is not fitted with an integral check valve, it can be used as asheath to cover the collapsed valve during withdrawal from the patient,thus preventing scratching of the vasculature on its way out.

IV. Imaging System for Implantation of Collapsible Cardiac Valve

[0142] Complex, remote surgery such as described above, requires asuitable device tracking and visualization system. Most MIS proceduresare performed on organs that do not involve considerable bleeding sincethe surgeon is oriented and guided only with his own vision, usingendoscopic video cameras. Using endoscopes in a bloody environment isnot convenient because blood is opaque. Optical visualization andlocalization inside the beating heart is simply impractical.

[0143] Such a system will therefore need real-time, high resolutionultrasound imaging, continuous X-ray fluoroscopy, or some combination ofboth. Real-time open magnet MRI is also an option, but the need for highstrength metallic instruments in this system makes MRI unlikely. X-rayimaging is undesirable because of the harmful radiation, and ultrasounddoes not currently have sufficient spatial resolution when operated in3-D mode and is unlikely to in the near future. Ultrasound imaging isalso susceptible to shadowing from dense, metallic objects. Innovativeimaging modalities alone, may not be sufficient for properly guiding thevalve replacement procedure. A 3-D visualization system, that integratesmultiple imaging modalities and real time device tracking, is thereforemost suitable. For instance, an ultrasonic catheter and device trackingsystem, analogous to that described in U.S. Pat. No. 5,515,853(incorporated herein by reference), would be very appropriate, if linkedto a powerful 3-D graphics engine that can simulate the position andmovement of the various objects as they are manipulated inside thepatient. Another device tracking system that could be used would employelectromagnetic localizer technology, such as that described in U.S.Pat. No. 5,546,951 (incorporated herein by reference). Other electrical,magnetic or image based localizer system can be used with similarfunction. To provide additional information, numerous images obtainedsimultaneously using ultrasound, X-ray or other imaging modalities couldbe integrated into this viewing environment, as described in U.S. Pat.No. 5,817,022 (incorporated herein by reference), to provide additionalfeedback regarding the true position of the objects. The imaging headsfor any optical, acoustic, radiographic or electromagnetic imagingsystems can be incorporated into the surgical platform for monitoring ofthe valve replacement procedure.

V. Other uses of device delivery system.

[0144] There is a growing number of surgical and therapeutic proceduresthat involve the delivery of a device or multiple devices to the insideof a body to a site of surgery or device deployment. To date, all ofthese systems employed a conventional catheter without the longitudinalsplit, and without the use of a surgical platform. Use of the presentinvention: (i) enables the delivery of larger devices to the target siteby the use of smaller catheters, and (ii) stabilizes the distal end ofthe catheter for much more precise, more controllable catheter-basedprocedures. Such a surgical platform can be used for ablation procedureswithin the ventricles and the atria by better stabilizing the catheters,for the delivery of larger endovascular prostheses or occluding devicesto stop internal bleeding, such as in cirrhotic liver vessels orventricular-septal defects. The surgical platforms for such applicationsdo not need to incorporate internal valves and can therefore besimplified into baskets or cages or articulating structures that simplylodge themselves against the appropriate anatomy, as shown in FIGS.9A-9C, in the case for atrial access. In this embodiment, the surgicalplatform 80 includes forked projections 81 that slide out of a maincatheter 82 and lodge themselves against appropriate cardiac anatomy,such as the commissures of the mitral valve 85. The “commissure” is ananatomic site, defined as the spot where the anterior leaflet 86 meetsthe posterior leaflet 87. These commissures are also located between theatrium 88 and the ventricle 89, which in themselves provide walls orsurfaces against which the projections 81 can be anchored.

[0145] The present invention has been described with reference to apreferred embodiment. Obviously, it will be appreciated by those skilledin the art that various additions, modifications, deletions andalterations will occur to others upon a reading and understanding ofthis specification, and may be made to such preferred embodimentswithout departing from the spirit and scope of the invention.Accordingly, it is intended that all such modifications and alterationsbe included within the scope of the invention as defined in thefollowing claims.

Having thus described the invention, it is now claimed:
 1. Acardiovascular valve system comprising: a permanent base unit attachableto tissue; and a collapsible valve engageable with said permanent baseunit, wherein said collapsible valve includes a collapsible frame havinga plurality of articulated struts, said collapsible frame movablebetween a collapsed position and an expanded position.
 2. Acardiovascular valve system according to claim 1 , wherein collapsiblevalve further includes an occluding member movable between an occludedposition and an open position, said occluding member supported by saidcollapsible frame.
 3. A cardiovascular valve system according to claim 2, wherein said occluding member includes at least one leaflet occluder.4. A cardiovascular valve system according to claim 1 , wherein saidarticulated struts are generally rigid.
 5. A cardiovascular valve systemaccording to claim 1 , wherein said permanent base unit includes areceptacle for receiving the collapsible valve.
 6. A cardiovascularvalve system according to claim 5 , wherein said receptacle includes aplurality of plates.
 7. A cardiovascular valve system according to claim1 , wherein said system further comprises at least one retaining memberfor retaining the engagement of said collapsible valve with saidpermanent base unit.
 8. A cardiovascular valve system according to claim7 , wherein said retaining member includes a gusset.
 9. A cardiovascularvalve system according to claim 7 , wherein said retaining memberincludes a slot.
 10. A cardiovascular valve system according to claim 7, wherein said retaining member includes a generally elastic retainingclip.
 11. A cardiovascular valve system according to claim 7 , whereinsaid retaining member includes a channel.
 12. A cardiovascular valvesystem according to claim 7 , wherein said retaining member includes agenerally rigid retainer.
 13. A cardiovascular valve system according toclaim 7 , wherein said collapsible frame includes articulating hookmembers, said articulating hook members engageable with said retainingmember.
 14. A cardiovascular valve system according to claim 13 ,wherein said articulating hook members are rotatable between anengagement position and a disengagement position.
 15. A cardiovascularvalve system comprising: a permanent base unit attachable to tissue,said permanent base unit including a receptacle; and a collapsible valveengageable with said receptacle, wherein said collapsible valve includesa collapsible frame having a plurality of articulated struts, saidcollapsible frame movable between a collapsed position and an expandedposition.
 16. A cardiovascular valve system according to claim 15 ,wherein said receptacle includes a plurality of plates.
 17. Acardiovascular valve system according to claim 16 , wherein saidplurality of plates are generally triangular.
 18. A cardiovascular valvesystem according to claim 17 , wherein said plurality of plates form avalve orifice.
 19. A cardiovascular system according to claim 15 ,wherein said collapsible valve includes at least one leaflet attachedwith said plurality of articulated struts.
 20. A cardiovascular valvesystem according to claim 15 , wherein said collapsible frame includesarticulating hook members, said articulating hook members engageablewith said permanent base unit.